This invention relates to a piston-operated dispenser unit for liquid or semi-liquid food products.
More specifically, this invention relates to a dispenser unit which is mounted on machines for making and instantaneously dispensing confectionery products in creamy or semi-liquid form.
The dispenser unit of the invention is advantageously suitable for mounting on machines for making and instantaneously dispensing frozen confectionery products such as soft ice cream served directly from the machine, yogurt ice cream or creamy ice cream cake and pastry fillings.
The dispenser unit of the invention can also be mounted on machines for making and instantaneously dispensing hot confectionery products such as chocolate, creams and the like.
For convenience of description and without limiting the scope of the invention, this specification refers expressly to machines for making and instantaneously dispensing frozen confectionery products (in particular, soft ice cream).
These machines usually have a product collection bin, a product processing cylinder located downstream of the collection bin, a dispenser unit comprising a tap mounted at the outlet of the cylinder and a cooling circuit for the product being processed in the cylinder.
More specifically, as is known, the main body of the tap comprises a duct having, at one end of it, an inlet mouth in communication with the processing cylinder, and, at the other end, an outlet mouth for dispensing the product made.
Slidably mounted inside the duct is a piston which is mobile between an open position and a closed position of the duct.
The piston is operated manually by the operator by means of a lever which is lowered to move the piston to the open position and raised to move the piston to the closed position.
The product is fed into the cylinder by a gear pump or a peristaltic pump or, alternatively, is gravity fed and, inside the cylinder, is processed and pushed towards the outlet mouth by a single- or double-spiral rotary stirrer.
Between one dispensing and the next, the tap lever must be reset. Furthermore, after each dispensing, the tap lever must always be brought to the raised position to prevent product from coming out when not required.
One drawback encountered during use is that the piston is not returned exactly to its closed position, causing an unwanted extra amount of product to be dispensed or to leak out. This is often due to the fact that the operator does not raise the lever all the way or, more rarely, does not raise it at all. The problem may, however, also be caused by slack in the piston-lever assembly preventing the piston and/or the lever from reaching the end of stroke position or causing it to return to a half open position.